1. Field of the Invention
The present invention relates to a light emitting device, and particularly to a flat light source unit which emits light progressing in a plane and a liquid crystal display device with the flat light source unit.
2. Discussion of the Related Art
Related art flat light source units provide non-luminescent display devices with light progressing in a plane. Liquid crystal display device are one of the non-luminescent display devices and use the flat light source unit as a backlight unit.
The flat light source unit uses an external electrode fluorescent lamp (EEFL) and a cold cathode fluorescent lamp (CCFL) as a light element. The EEFL and CCFL are tube type lamps which consume relatively large power during emission of light. In addition, the amount of light emitted from the tube type lamps varies very greatly according to temperature.
To address the disadvantages of the tube type lamps, a flat light source unit using a light emitting diode (LED) array as the light device has been suggested. LEDs consume quite a low power compared to the tube type lamp. The deviation in the amount of radiated light of the LED according to the change of temperature is remarkably small compared to the tube type lamp. In terms of the above, recent flat light source units mainly use LEDs.
The LED array of a flat light source unit includes a plurality of LEDs arranged on a printed circuit board (hereinafter, referred to as the “PCB”). The PCB receives a drive voltage to be supplied to the LEDs, from a light source drive circuit unit. To this end, the PCB of the LED array is electrically connected to the light source drive circuit unit via a connection cord.
The connection cord is typically attached to the PCB by soldering so as to be electrically connected to a conductive pattern on the PCB. The soldered connection cord is frequently detached from the PCB due to an excessive force or the carelessness of a worker until the LED array is installed in a case (or housing) of the flat light source unit.
A shrink tube for encasing a connection portion between the connection cord and the PCB is used to prevent the detachment of the PCB of the connection cord. The shrink tube requires a plurality of processes of encasing an end portion of the connection cord using the shrink tube before soldering, heating the shrink tube after the soldering, widening an end of the heated shrink tube, and encasing part of the PCB using the widened shrink tube. Accordingly, the manufacturing time of the flat light source unit and the LCD device with the flat light source unit increases and the manufacturing costs are raised. In addition, since the shrink tube encompasses a part of the PCB, the size of the flat light source unit as well as the LCD device with the flat light source unit is increased as much as the thickness of the shrink tube.
In another method, as the connection cord is inserted into a connection slot provided on the PCB, the connection cord is electrically connected to the conductive pattern of the PCB. The connection cord inserted in the slot may be easily detached from the PCB due to the carelessness of a worker during the process of manufacturing the flat light source unit and the LCD device with the flat light source unit and an external impact after the flat light source unit and the LCD device with the flat light source unit are manufactured. As a result, the flat light source unit having the slot insertion type connection cord and the LCD device with the flat light source unit are easily broken down so that reliability of the flat light source unit and the LCD device with the flat light source unit is deteriorated.